题解 | 小红的01子序列构造（easy）

#include <iostream>
using namespace std;

void answer(string str, long long int k)
{
    int len = str.length();
    int left = 0, right = 0;
    long long int count = 0, cnt0 = 0, cnt1 = 0;

    while ( str[left] != '0' ) left++;
    right = left;
    while ( str[right] != '1')
    {
        right++;
        cnt0++;
    }
    cnt1 = 1;
    count = cnt0;

    while ( left < len && right < len )
    {
        
        if ( count == k )
        {
            cout << left + 1 << " " << right + 1 << endl;
            return;
        }
        else if ( count < k )
        {
            while ( str[++right] != '1' && right < len )
            {
                cnt0++;
            }
            count += cnt0;
            cnt1++;
        }
        else 
        {
            count -= cnt1;
            while( str[++left] != '0' && left <= right )
            {
                cnt1--;
            }
            cnt0--;
        }
    }
    cout << "-1" << endl;
}

int main() {
    long long int n, k;
    string str;
    while (cin >> n >> k >> str) { // 注意 while 处理多个 case
        answer(str, k);
    }
}
// 64 位输出请用 printf("%lld")